DCR：On a given design, as inductance (turns of wire) goes up, so does the DCR.

If the permeability of the core is increased, the number of windings can be reduced, and DCR will go down.

Rated Current：On a given design, as inductance (turns of wire) goes up the rated current goes down.

If the permeability of the core is increased, the number of windings can be reduced and rated current will go up.

Incremental Current：On a given design, as inductance (turns of wire) goes up, the incremental current goes down.

If the permeability of the core is increased, the number of windings can be reduced and incremental current may increase or decrease.*

*If the increased permeability decreases the point at which the core saturates, the actual incremental current can go down.

SRF：On a given design, as inductance (turns of wire) goes up, the distributed capacitance will also go up, and the SRF will go down.
If the permeability of the core is increased, the number of windings can be reduced, and SRF will increase (less distributed capacitance).
“Q”：On a given design, as inductance (turns of wire) goes up, the Q goes down.
A higher Q generally indicates an inductor that is a more selective filter. Inductors used in RF circuits usually have high Q’s so they can be more frequency selective.
A lower Q generally indicates an attenuation over a broader range of frequencies. A ferrite bead has a low Q and is thus considered a broadband filter.

Litz Wire is composed of multiple individually insulated strands that are either woven or bundled together in such a way that each strand occupies every possible position within the overall cross-sectional area of the wire. This unique arrangement ensures that the current flowing through each strand is evenly distributed in higher frequency, as the design of the wire balances the flux linkages and reactance among the individual strands. Essentially, a Litz conductor exhibits significantly lower AC losses compared to solid-wire conductors, making it particularly advantageous as the operating frequency rises.

Skin effect is the tendency for alternating current to flow near the surface of the conductor in lieu of flowing in a manner that utilizes the entire cross-sectional area of the conductor.

Eddy current losses are present in both the magnetic core and winding of an inductor. Eddy currents in the winding (or conductor) contribute to two main types of losses:
• Losses due to proximity effects.
• Skin effects.
As for the core losses, an electric field around the flux lines in the magnetic field is generated by alternating magnetic flux. This will result in eddy currents if the magnetic core material has electrical conductivity. Losses result from this phenomenon since the eddy currents flow in a plane that is perpendicular to the magnetic flux lines.

Core losses are caused by an alternating magnetic field in the core material. The losses are a function of the operating frequency and the total magnetic flux swing. The total core losses are made up of three main components: hysteresis, eddy current and residual losses. These losses vary considerably from one magnetic material to another. Applications such as higher power and higher frequency switching regulators and RF designs require careful core selection to yield the highest inductor performance by keeping the core losses to a minimum.

The operating temperature is different from the storage temperature in that it accounts for the component’s self temperature rise caused by the winding loss from a given DC bias current. This power loss is referred to as the “copper” loss and is equal to:

Power Loss = (DCR) （）

The power loss is equal to the square of the current multiplied by the resistance of the wire (I2 R). This power loss is transferred into heat.

The impedance of an inductor is the total resistance to the flow of current, including the AC and DC component. The DC component of the impedance is simply the DC resistance of the winding. The AC component of the impedance includes the inductor reactance. The following formula calculates the inductive reactance of an ideal inductor (i.e., one with no losses) to a sinusoidal AC signal:

Z = XL = 2πfL

L is in Henry and f is in Hertz. This equation indicates that higher impedance levels are achieved by higher inductance values or at higher frequencies. Skin effect and core losses also add to the impedance of an inductor.

The Q value of an inductor is a measure of the relative losses in an inductor. The Q is also known as the “quality factor” and is technically defined as the ratio of inductive reactance to effective resistance, and is represented by:

Since X_L and Re are functions of frequency, the test frequency must be given when specifying Q. X_L typically increases with frequency at a faster rate than Re at lower frequencies, and vice versa at higher frequencies. This results is a bell-shaped curve for Q vs frequency. Re is mainly comprised of the DC resistance of the wire, the core losses and skin effect of the wire. Based on the above formula, it can be shown that the Q is zero at the self-resonant frequency since the inductance is zero at this point.

The frequency at which the inductor’s distributed capacitance resonates with the inductance. It is at this frequency that the inductance is equal to the capacitance and they cancel each other. The inductor will act purely resistive, with a high impedance at the SRF point. Also, the Q of the inductor is equal to zero at the SRF point since the inductive reactance is zero. The SRF is specified in MHz and is listed as a minimum value on product data sheets.

The permeability of a magnetic core is the characteristic that gives the core the ability to concentrate lines of magnetic flux. The core material, as well as the core geometry, affect the core’s “effective permeability”. For a given core shape, size and material, and a given winding, higher permeability magnetic materials result in higher inductance values as opposed to lower permeability materials.

The level of continuous DC current that can be passed through the inductor. This DC current level is based on a maximum temperature rise of the inductor at the maximum rated ambient temperature. The rated current is related to the inductor's ability to minimize the power losses in the winding by having a low DC resistance. It is also related to the inductor's ability to dissipate this power lost in the windings. Thus, the rated current can be increased by reducing the DC resistance or increasing the inductor size. For low frequency current waveforms, the RMS current can be substituted for the DC rated current. The rated current is not related to the magnetic properties of the inductor.

The DC bias current flowing through the inductor which causes the inductance to drop by a specified amount from the initial zero DC bias inductance value. Common specified inductance drop percentages include 10% , 20 % and 30%. It is useful to use the 20% inductance drop value for ferrite cores and 30% for powdered iron cores in energy storage applications. The cause of the inductance to drop due to the DC bias current is related to the magnetic properties of the core. The core, and some of the space around the core, can only store a given amount of magnetic flux density. Beyond the maximum flux density point, the permeability of the core is reduced.

The DC resistance of the inductor winding measured with no alternating current. The DCR is most often minimized in the design of an inductor. The unit of measure is ohms.

That property of a circuit element which tends to oppose any change in the current flowing through it. The inductance for an inductor is influenced by the core material, core shape and size, the turns count, and the shape of the coil. Inductors most often have their inductances expressed in microhenries (μH). The following table can be used to convert units of inductance to microhenries.

1 henry (H) = 10⁶ μH

1 millihenry (mH) = 10³ μH

1 microhenry (μH) = 1 μH

1 nanohenry (nH) = 10^-3 μH

Magnetic powder core is a material that has an inherent distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials, such as ferrites. This characteristic allows a higher DC current level to flow through the inductor before the inductor saturates. Magnetic powder cores are made of iron and some other material such as Si, Al or Ni. The particles are insulated from each other, mixed with a binder (such as phenolic or epoxy) and pressed into the final core shape. CODACA high current power inductor such as CSBX，CSBA and CPEX are made of magnetic powder core.

The voltage induced across an inductor by a change of current is defined as:V = L di/dt. Thus, the induced voltage is proportional to the inductance value and the rate of current change.

Power inductor is designed to resist changes in AC current. Inductors are often referred to as “AC resistors”. The ability to resist changes in current and store energy in its magnetic field account for the bulk of the useful properties of inductors. Current passing through an inductor will produce a magnetic field. A changing magnetic field induces a voltage which opposes the field-producing current. This property of impeding changes of current is known as inductance.

The shrink tube does not have any effect on the electrical performance of the inductor, but it can protect the coil from damage, and it can also improve the voltage resistance of the inductor.

The leakage inductance of the bifilar winding will be smaller. Because the coefficient of the bifilar winding will be higher than that of the sectional winding, and the bifilar winding will be evenly distributed on the core, which can improve the leakage phenomenon.

High current power inductors are usually used in high power applications which flow relatively high current through, so there are strict requirements for the effective cross-sectional area of wire and DCR.

The effective cross-sectional area of the round enameled wire is smaller than that of the flat wire. There is a gap between the turns of the round wire, and the utilizations of the winding window of the magnetic-core insufficient. Therefore, with the same size, the current capacity of the round enameled wire product is smaller than that of the flat wire, and there will be a problem of temperature rise. That is why engineers design high current power inductor with flat wire, not round wire.

The Q value is the quality factor of an inductor, which is used to show the relationship between the energy stored and the energy consumed by the inductor. Its mathematical expression is listed as follows:

Q value=storage energy/consumption energy=XL/R=2πf*L/R

XL: inductive reactance (Ω)

R: resistance (Ω)

f: frequency (Hz)

L: inductance value (H)

From definition of Q value, it is obvious that the higher the Q value, the lower loss in digital communication circuits. The size of Q value directly affects the data transmission speed. However, there are three variables that determine the Q value, namely R: resistance (Ω) ,F: frequency (Hz) , L: inductance value (H).

All inductors have capacitance between their windings, which is called distributed capacitance.

As the frequency increases, the inductor's inductive reactance (XL) and AC resistance (R) will increase at the same time. When the frequency is higher than the limit that the inductance can withstand, the inductive reactance of the inductor will decrease sharply until it disappears, and it is characterized by the capacitive load. The frequency point (XL = 0) at which this phenomenon occurs in the inductor is called the self-resonance frequency point of the inductor, that is, before this frequency, the inductance is inductive, L > 0, and after this frequency, it is capacitive, L < 0.

When designing electronic circuits, especially high-frequency circuits, engineers have to consider about the normal working frequency of the circuit and to propose that the SRF must be greater than a certain limit value to ensure the normal operation of the circuit.

The factors affecting the SRF value of inductor include magnetic-core material, wire diameter, and the number of turns (L value). Because the general application frequency of high-current inductors is under 1 MHz, this frequency range is far from reaching the self-resonant frequency point, so there is no SRF in the specification.

The essential difference between soft saturation and hard saturation lies in magnetic-core material. The soft saturation inductor is made of powder-core, and the hard saturation inductor is made of the ferrite-core. The DC bias characteristics of the two are different, and the inductor should be selected according to its specific applications. The ferrite-core with hard saturation is more suitable for higher frequency, and the powder-core with soft saturation is more suitable for lower frequency (Less than 300kHz）.

The size of the current changed depending on the time that current is applied. For any applications which a current exceeding the rated current required, please contact CODACA.

Inductor losses include AC loss and DC loss. When designing an inductor in a power supply, engineers will calculate the AC loss and DC loss based on the detailed electrical conditions. When the AC loss and DC loss are nearly equal in a balanced state, engineers can get a reasonable design with the smallest total loss. CODACA offers design tools for easily predicting frequency effects. To estimate core loss, conductor loss, and temperature rise of our power inductors, please use the Power Inductor Loss Comparison.

① The saturation current of an inductor is smaller than the operation current in the power supply, and the core of the inductor become saturation. And then the output current will have ripples;

② Inductance value is not enough, and the inductor can not store enough energe, then resulting in high ripple current of output in power supply.

A: The calculation of inductance value is similar to resistance calculation if the inductors are used in series or parallel.

① The total inductance will be increased when an inductor is used in series, and the total inductance is the sum of all inductors. (L = L1 + L2 + L3 +...)

② The total inductance will be decreased when an inductor is used in parallel, but the current will be higher. The total current is the sum of the currents in each inductor, it can be used in circuits with a higher current.

L=1/(1/L1+1/L2+1/L3+1/L4+……)

Power inductor manufacturer usually define the tolerance with specific letters in inductor naming. Such as the following tolerances of power inductors, J: 5% ; K: 10% ; M: 20% ; N: 30%.

Selecting a right inductor will effect efficiency of power supply. However, the power needs to be converted into specific parameters such as input voltage, output voltage, switching frequency, ripple current, output current.

A power inductor doesn’t have defined the rated voltage, because most of the inductors are used in the low-voltage DC-DC convector. For any application in which inductor high-voltage is required, please contact CODACA.

Rated current is the maximum current that can SAFELY pass through the inductor.

The weight of a CODACA part is typically specified on the datasheet.

Tape-and-reel information of all CODACA’s products can be found in products’ datasheet with the dimensions at CODACA’s website.

It's difficult for CODACA to recommend a specific minimum spacing between inductors. Electromagnetic fields created by inductors generally interact only with metallic surfaces or other inductors in close proximity. However, the extent of interaction between inductors depends on the current (frequency, waveform shape and magnitude ), the orientation to each other, and the distance between inductors. (Remind: Orienting the axes of inductors perpendicular to each other, rather than parallel, to get a minimum interaction.)

Yes. CODACA provides a reflow soldering profile in each datasheet. The optimal reflow profile for a circuit board assembly depends on soldering materials, soldering amount, flux, temperature limits of each soldered component, heat transfer characteristics of the circuit board and component materials, and the layout of all components.

Magnetic shielding is to reduce the amount of magnetic flux generated outside an inductor, in terms of reducing the likelihood of radiating energy to nearby components or circuit board traces causing EMI. Whether a shield is necessary or not depends on the proximity of other components and how field interactions would affect the circuit's performance. Field interactions are challenging to prototyping while measurement of the final circuit design is recommended. In addition to reducing radiated fields, magnetic shielding typically helps to achieve more inductance per given size of an inductor.

For 30°C / 85% relative humidity maximum, CODACA’s parts are good indefinitely, based on MSL=1, CODACA’s parts are good for one year in packaging.

These safety standards are most commonly apply to complete electronic assemblies, such as power supplies, computers, modems, and televisions, but not specifically to CODACA’s inductors. In most cases, CODACA’s products are usually evaluated as parts for finished products built by its customers. Inductors are not required to provide above certificated individually.

RMS current ratings are power ratings for CODACA’s inductors, derived by applying DC or low frequency AC current to measure the resultant temperature rise. This allows for an accurate determination of temperature rise vs. RMS current, which can easily be related to temperature rise vs. power loss: Power Loss = Irms2 × DCR.

Meanwhile,CODACA’s inductor losses include skin effect, high-frequency core loss and proximity effect, which can add to the temperature rise. While these losses are dependents and should be verified in situations, CODACA offers design tools for predicting frequency effects. To estimate core loss, conductor loss, and temperature rise of ours power inductors, use the Power Inductor Loss Comparison.

Inductors do not have a functional polarity, which make they work equally in either direction. Polarity is not very important in the vast majority of end-use circuits. It has been reported that some inductors perform better when mounted in one particular orientation, due to interaction with nearby components or ground plane conductors. Any asymmetrical performance is very much related to a function of the application, especially board layout. For any applications in which inductor polarity is critical, please contact CODACA.

There are many kinds of toroid inductors with different characteristics. We could compare a high current power inductor with a toroid inductor same kind of core material in the same application.

① The utilization rate of winding window area of the toroid-core inductor is lower than the EQ -core high current power inductor. For the same electrical performance, the volume of high current power inductor with EQ cores will be relatively smaller than toroid inductor.

② The high power toroid-core inductor can’t realize automatic assembly because the wire is too thick and can only be wound by hand.

③ The high current inductor with EQ-core is designed with flat wire, the effective cross-section is bigger than the round wire, the DRC is lower thant that of the toroid core inductor, so it can withstand higher current.

④ The AE value of the high current inductor with EQ-core is higher than that of the toroid core inductor. The high current inductor has better DC bias ability than the toroid core inductor.

⑤ The toroid core inductor coil is exposed, which has leak magnetic flux to affect other component in PCB when power supply is working. While, the coil of high current power inductor with EQ-core is wrapped inside with excellent anti-interference ability.

① For high current power indutors, the magnetic-core with coating is a method of insolation improvement to increase the withstand voltage of products.
② For molding power chokes, coating can protect the magnetic powder and prevent the product from rusting.

There is no method to 100% eliminate the noise. Instead, it can be suppressed or weakened. The source of noise is usually caused by a mechanical resonance in the component that is excited by the electrical conditions of the circuit, known as magnetostriction, and does not indicate a defect in the part. It depends on the application conditions and is not always possible to eliminate by changes to the inductor.

Changing the switching frequency is the best way to eliminate the noise. Applying a dampening material (electronic-grade encapsulant, potting compound, etc.) may decrease the produced sound level while the increased mass of a larger component may dampen or shift the resonance to a different frequency.

① The current margin of a power inductor is insufficient. The current over the power inductor in applications is higher than the rated current of inductor which will casue high temperature rise.
② The alternating current or ripple current in the circuit is too high, and the magnetic core loss is serious, resulting in heating.
③ The application frequency is very high, but engineers won’t select the right core and wire during the inductor design.

Base on the high frequency and high ripple current applications, the core losses and the AC losses of copper wires should be considered in the design of power inductors. Such as ferrite core and low permeability powder core are suitable for high-frequency applications. Besides, the influence of skin effects should be considered, flat wire or litz wire design can also be used to reduce AC losses.

The weight could be found in datasheet for each product. In general speaking, a weight range may be given that covers the entire series. If you can not find the weight information in the datasheet, please contact us through info@codaca.com

Thermal resistance is not specified for CODACA inductors and transformers because they are mostly open-frame style.

To calculate a roughly thermal resistance, divide the temperature rise due to Irms current (e.g., 40°C rise) by the power required to generate that rise (Power = DCR × Irms2).

So you could get a value by the following calculation:

Rth (in °C/W) = 40°C ÷ (DCR × Irms2) (remark: DCR is in Ohms and Irms is in Amps).

The tape-and-reel specifications could be found in datasheet for each products.

Yes, we could provider the samples with empty pockets sealed with cover tape even you not order one whole reel, please remark the information while sending inquiry to CODACA.

The optimal reflow profile for a circuit board assembly depends on solder material and amount, flux, temperature limit of each soldered component, heat transfer characteristics of the circuit board and component materials, and the layout of all components. Therefore, recommended reflow profile information can be found in the datasheet for each SMD component.

Many factors influence solder wetting: solder material and amount, flux, temperature limit of each soldered component, heat transfer characteristics of the circuit board and materials, and the layout of all components.

Reducing the amount of magnetic flux generated out of the inductor is the purpose of using shielded power inductor, in turn reducing the probability of radiating energy to nearby components or circuit board traces causing electro-magnetic interference (EMI). Whether a shielded inductor is necessary depends on the proximity of other components and how field interaction would affect the circuit's performance. Field interactions are always challenge for power supplier design engineers, and that's why we suggest it's needed to have measurement of the final circuit design. In addition to reducing radiated fields, magnetic shielding normally contributes to the inductance of the component, helping to achieve higher inductance in a power inductor.

CODACA provides many online design tools and application notes to help you select the correct part.

Design Tools page Quickly check optimal part with these easy-to-use tools.

Power inductor finder View the products that fit your application.

Power Inductor Loss Comparison Compare the losses and find out the best inductor for you.

DCR Temperature Calculator Get a reference of the DCR value in the specific temperature

Reference Design Inductor Finder Get a list of CODACA parts suitable for 1000s of IC reference designs. Cross Reference Inductor Finder Find CODACA alternatives to other manufacturers’ part numbers.

That type of noise is usually due to a mechanical resonance in the component that is excited by the electrical conditions of the circuit, known as magnetostriction, and does not indicate a failure in the component. It is very dependent on the application conditions and can not 100% eliminate by change another inductor.

Changing the switching frequency is often recommend to eliminate the noise. Apply a dampening material such as electronic-grade encapsulant, potting compound, etc.

Under the same condition of permeability: the FeSi core has the best DC bias capability while the Sendust Powder Core is lower loss when the frequency is higher than 250 kHz.

If you would like a sample, please send inquiries to us info@codaca.com.

Please refer to our product list for compliance with AEC-Q200 catalogue, you could also search CODACA AEC-Q200 compliance products page on line .

The metal magnetic material features small inductance changes by temperature increasing and does not reach magnetic saturation as easily as ferrite, and the current value based on inductance change is significantly different from that of a ferrite core.

As a ferrite core exhibits higher resistance compared to a metal powder material, it has small eddy current loss and more often used at relatively higher frequencies.

As a metal powder core shows a better of soft saturation and usually recommend used in automotive and lower loss power circuit. With metal powder core and flat wire design, it could get less losses and stable electrical performance in the high temperature. Learn more about this new type power inductor CPEX Family High Current Power Inductor_CODACA.

The exterior of the product is covered with magnetic material. This prevents magnetic flux leakage inside the product from leaking outside. It also makes the product better resistance to external influences.

For shielded and unshielded power inductors selection, CODACA has published the PDF ‘Power Inductor Selection Guide’.

When DC bias current is applied to an inductor, magnetic permeability decreases as the magnetic material approaches to saturation, it's reflected in the reduction in inductance. This is referred to as the DC bias characteristic.

In our website, as remarked in each datasheet, you can also refer to a DC bias characteristic curve on the detailed information page.

CODACA website offers datasheet to help you check the inductance value in the characteristics graph. If you cann’t find a characteristic graph in the desired detailed information page, please contact us through our website.

These are the inductances expressed in a unit of microhenry (μH)

The first two digits indicate significant figures and the third digit a multiplier. When there is an "R", it indicates a decimal point, and all numbers are significant figures.

For example:

R33 = 0.33 μH

2R2 = 0.22 μH

100 = 10 x 100 =10 μH

101 = 10 x 101 =100 μH

Loss has a direct effect on the efficiency of the power supply. Consequently, we recommend that selecting an inductor with low loss(DC resistance and AC resistance at the operating frequency). Such as flat wire or litz wire products, for more information about power loss in certain operation condition, please select inductor by our online design tool Power Inductor Loss Comparison.

Inductors have the following specific application purposes:

a.Filtering necessary signals and unnecessary signals.

b.Smoothing voltage in a power circuit.

c.Matching impedance in a high frequency circuit.

Core and winding loss data for many of our power inductors is included in our online design tool Power Inductor Loss Comparison.

Please refer to https://www.codaca.com/DesignTool_Power-Inductor-Loss-Comparison.html

Coil loss:

①DC loss comes from DCR DC resistance.

②AC loss, the application environment of inductor is not constant DC, but superimposed current with AC component. AC winding loss is more complicated and may include the effects of increased resistance at higher frequency due to both skin effect and proximity effect. ESR (effective series resistance) or ACR (AC resistance) curves may show some of the increased resistance at higher frequency. The effective method to reduce the ACR of the wire is to use flat wire, Litz wire, etc. The wire structure can keep the original effective cross-sectional area as much as possible during high frequency application, such as CODACA's flat wire high current power inductor.
Magnetic core loss:

③Eddy current loss, after the coil was energized, the magnetic field will be changed with the change of the current. Because the resistance of the magnetic core is not infinite, an electric field will be generated. The current works on the resistance of the magnetic core and generates heat, resulting in loss.

④Hysteresis loss, under the action of the external magnetic field, the magnetic domain inside the magnetic core must be magnetized in the same direction, and must overcome the frictional force between the magnetic domain wall and the magnetic domain wall. Which is the cause of hysteresis loss.

⑤Residual loss, during the magnetization process of the magnetic core, it does not immediately change to its final state with the change of magnetization. It is necessary to overcome certain obstacles. There is a time difference in this process, which is the cause of residual loss.

Generally, it is not recommended to use the power inductor under the condition that the operating current exceed the rated current of the inductor. Because while using under this condition, the loss of the inductor will reach a certain level, which means that the efficiency of the power supply will decrease. However, if the power supply has additional cooling measures in the design, and the requirements for power efficiency are not high, it can also be adjusted and used according to the actual application.

If the working current is greater than the temperature rise current and less than the saturation current, such as CODACA's CSBX0630-R10M, the saturation current is 70A, the temperature rise current is 23A, and the working current is 30A, then in this case, there is still has a distance to go before saturation. So it will not cause the inductor to fail, but it is higher than the nominal temperature rise current, plus the magnetic loss and AC loss, obviously the overall temperature rise (actual temperature - ambient temperature) will be exceed 40 ℃, and the power inductor still work under condition of -40℃~+125℃ which is not exceeding this temperature range.